Figure 1
APS/Alan Stonebraker

Figure 1: Schematic experimental geometry of Williams et al. The Josephson effect between the superconducting (SC) Ti/Al leads is carried by proximity-effect superconductivity (blue region) in the surface state of the 3D topological insulator (TI)  Bi2Se3. The red lines are flux lines of an applied magnetic field; the magnetic field through the superconducting leads is omitted for simplicity. Under certain conditions, a bound Majorana excitation in the proximity-effect region can lead to an unusual current-phase relation that is manifested in the dependence of critical current on magnetic field.